Assignment 3 - os_getChunkSize correct implementation

* os_getChunkSize returns 0 if given chunk is free
* changed comments
* added helper function for missing functionality in os_getChunkSize
* memory strategies changed to use helper function
Assignment 3 - Memory driver patches

* os_initHeaps now works with heap array
* removed getEndOfChunk and refactored os_getChunkSize and
os_freeProcessMemory
* refactored all memory alloc strategies to be more efficient and work
correctly